Role of intercellular communication in pathogenesis of diabetic retinopathy

项目摘要 本研究的总体目标是确定是否维持连接蛋白43(Cx43)介导的间隙 视网膜连接细胞间通讯(GJIC)和Cx43半通道(HC)活动 糖尿病患者毛细血管对视网膜血管细胞丢失的保护作用 以及与糖尿病视网膜病变(DR)相关的血管通透性。确凿的证据表明 视网膜血管细胞GJIC活性降低可能是糖尿病视网膜病变动态平衡破坏的原因之一 (1-4)。我们已经证明，主要的缝隙连接蛋白Cx43的表达是 高糖(HG)状态下视网膜血管细胞表达下调 GJIC活性(3，4)，导致视网膜血管细胞丢失和毛细血管渗漏。初步数据 提示HG降低Cx43HC活性并引发细胞凋亡(5)。最近，我们观察到， 维持细胞-细胞偶联抑制HG诱导的细胞凋亡和细胞单层过度通透性 体外培养(6)。基于这些发现，我们假设预防高血糖诱导的Cx43 下调调控和GJIC活性将促进血管动态平衡，恢复Cx43 HC活性和 Cx43磷酸化，最终防止DR的视网膜血管细胞丢失和毛细血管渗漏。 这一假说得到了来自前一个资助期的研究结果的支持，这些发现表明：(I)HG诱导 Cx43表达下调导致内皮细胞屏障紧密连接的破坏 降低ZO-1和occludin表达(7，8)，恢复Cx43表达(7)和间隙 连接偶联抑制HG诱导的视网膜细胞凋亡和细胞单层通透性 内皮细胞(6)；(Ii)Cx43在人视网膜中表达下调，且视网膜的严重程度 血管细胞损失与Cx43下调的程度有关(9)。这一假设也是 关键的初步数据支持Cx43磷酸化在S368和S373发生负变化 影响GJIC和HC活动中的Cx43功能。此外，有报道指出，ZO-1，a 紧密连接的组成部分，直接与Cx43(10)相互作用，并调节Cx43介导的GJIC 活动(11、12)。在观察到HG/糖尿病导致视网膜血管细胞中ZO-1减少后(13)，我们 建议研究Cx43下调、损害GJIC、改变HC活动以及 Cx43磷酸化改变促进视网膜血管细胞丢失和紧密连接功能障碍 血管通透性。预计这些发现将为我们提供有价值的见解，让我们了解 视网膜血管细胞丢失和毛细血管渗漏，以及预防视网膜血管病变的潜在策略 杜克博士。

Project Summary The overall goal of this research is to establish whether maintenance of connexin 43 (Cx43)-mediated gap junction intercellular communication (GJIC) and Cx43 hemichannel (HC) activity in the retinal capillaries of diabetic patients plays a protective role against the development of retinal vascular cell loss and vascular permeability associated with diabetic retinopathy (DR). Substantial evidence suggests that reduced GJIC activity in retinal vascular cells may contribute to the breakdown of homeostatic balance in DR (1-4). We have shown that the expression of Cx43, the principal gap junction protein, is downregulated in retinal vascular cells in high glucose (HG) condition with concomitant reduction in GJIC activity (3, 4) that contributes to loss of retinal vascular cells and capillary leakage. Preliminary data indicate HG reduces Cx43 HC activity and trigger apoptotic cell death (5). Recently, we observed that maintenance of cell-cell coupling inhibits HG-induced apoptosis and excess cell monolayer permeability in vitro (6). Based on these findings, we hypothesize that preventing hyperglycemia-induced Cx43 downregulation and GJIC activity would promote vascular homeostasis, restore Cx43 HC activity and Cx43 phosphorylation, ultimately preventing loss of retinal vascular cells and capillary leakage in DR. The hypothesis is supported by findings from previous funding period that showed (i) HG-induced downregulation of Cx43 expression contributes to the breakdown of endothelial barrier tight junctions by reducing ZO-1 and occludin expression (7, 8) and that restoration of Cx43 expression (7) and gap junction coupling prevents HG-induced apoptosis and cell monolayer permeability in retinal endothelial cells (6); (ii) Cx43 expression is downregulated in human retinas, and that the severity of retinal vascular cell loss is linked to the extent to which Cx43 downregulation develops (9). The hypothesis is also supported by key preliminary data that Cx43 phosphorylation is altered at s368 and s373 negatively impacting Cx43 functionality in GJIC and HC activity. Additionally, reports indicate that ZO-1, a component of the tight junction, interacts directly with Cx43 (10), and regulates Cx43-mediated GJIC activity (11, 12). Having observed ZO-1 to be reduced in retinal vascular cells by HG/diabetes (13), we propose to examine whether Cx43 downregulation, compromised GJIC, altered HC activity, and altered Cx43 phosphorylation promotes retinal vascular cell loss and tight junction dysfunction in vascular permeability. Findings are expected to provide valuable insight into a novel mechanism underlying retinal vascular cell loss and capillary leakage, and a potential strategy to prevent retinal vascular lesions in DR.